A Physicist’s Farewell to Stephen Hawking

Stephen Hawking was a scientific and cultural revolutionary. He saw the cosmos as no one before him had—and he could explain it to the masses, too.

Photograph by Santi Visalli / Getty

Stephen Hawking delighted in reminding audiences that he was born three
hundred years to the day after the death of Galileo, on January 8, 1942.
Imagine how Hawking would have reacted could he have known that he would
die on March 14, 2018—the hundred and thirty-ninth anniversary of Albert
Einstein’s birth.

I never got to know Professor Hawking, and yet I found myself mourning
the news of his passing as if I had lost a close colleague. Like so many
people of my generation, I grew up in a world in which Hawking’s name
was nearly as familiar as Einstein’s. In one way or another, I’ve been
grappling with his ideas for my entire career.

Hawking’s breakaway best-seller, “A Brief History of Time,” appeared in
1988, while I was in high school. By that time, I was already immersed
in popular books about the wonders of modern physics; the eighties saw a
boom in high-quality, inexpensive paperbacks, inviting readers to sample
some of the choicest mysteries of quantum
theory or admire the austere grandeur of Einstein’s general theory of
relativity.
Yet the release of Hawking’s book felt different. It became a sensation,
sought by people who had never noticed the raft of earlier books.
Hawking’s was a book to own and, for some, to read.

“A Brief History of Time” offered a tour of Hawking’s most significant
contributions to the field. His earliest efforts centered on relativity,
the work that had thrust Einstein himself into the spotlight, decades
earlier. According to the theory, space and time are as wobbly as a
trampoline. They can bend or
distend in the presence of matter and energy. Their curvature, in turn, gives
rise to all the phenomena we associate with gravity. Gravitation, in
this line of thinking, is not a force—the outcome of one object tugging
on another, as described by Isaac Newton’s equations—but a mere
consequence of
geometry.

Hawking’s first major contribution, which he began to develop in his
Ph.D. dissertation, at the University of Cambridge, was essentially to
push Einstein’s idea until it broke. What if matter were to become
packed so densely within a region of space that space-time itself
ruptured? Hawking, along with his colleague Roger Penrose, clarified the
conditions under which solutions to Einstein’s equations must devolve
into a “singularity,” quite literally a point of no return. The
Penrose-Hawking singularity theorems, as they came to be known, indicate
that under extreme conditions—in the centers of black holes, say, around
which space and time warp so intensely that not even light
escapes—space-time can simply end, a cosmic variant of Shel
Silverstein’s sidewalk.

The singularity theorems apply to so-called classical space-times—that
is, to descriptions of space and time that ignore quantum theory, that
other great pillar of modern physics. Soon after Hawking completed his
Ph.D., in 1966, he began to attack questions at the troublesome boundary
between relativity, which describes the behavior of the largest objects
in the cosmos, and quantum theory, which governs matter at the atomic
scale. He stumbled upon his most famous finding in the
mid-nineteen-seventies, while puzzling through scenarios in which pairs
of quantum particles might find themselves near a black hole. If one
were to fall in while the other escaped, Hawking suggested, the black
hole would appear, to a distant observer, as if it had emitted
radiation—precisely what black holes were not supposed to allow. In
other words, “black holes ain’t so black,” as he put it in “A Brief
History”: they glow. What’s more, this radiation could shape a black
hole’s fate. In astronomical timescales, the black hole could evaporate,
its once-enormous mass seeping out as cosmic static.

These puzzling ideas—equal parts bizarre and exciting—spawned many
others, some of which continue to challenge the physics community to
this day. Theoretical physicists still grapple with whether information
tossed into a black hole really disappears forever. Must it be scrambled
beyond any possible reconstruction, with only a meaningless bath of
radiation remaining? Such a process would violate quantum theory, for
which a sacrosanct rule is that information can be neither created nor
destroyed. Scores of theorists have turned Hawking’s arguments around
and poked them from every angle, trying to find where the weak joint
might lie in the uneasy combination of quantum theory and relativity.
Meanwhile, closer to my own research, Hawking’s ideas about the Big Bang
and whether our universe could have emerged from an initial singularity
continue to animate studies in cosmology.

Famously, Hawking’s descriptions of black holes and the Big Bang in “A
Brief History of Time” came interlaced with stories of his personal
life. He was diagnosed with the degenerative disease amyotrophic lateral
sclerosis (A.L.S.) in 1963, at age twenty-one—just as he was beginning his
doctoral studies—and was expected to live only a few more years. In his
book, Hawking wrote of his determination to carry on, bolstered by
meeting Jane Wilde (whom he married, in 1965) and, soon, by the arrival
of their three children. Surely these triumphs—the sheer, stubborn fact
that Hawking continued to live—drove the fascination with his book just
as much as his clever descriptions of warping space-time did.

Propelled by the book’s popular success, Hawking rapidly became a
full-blown celebrity. He kept up a remarkable travel schedule even as
the effects of his A.L.S. became more severe. In October, 1999, he visited
Harvard for three weeks, just as I was finishing my Ph.D. there. Lines snaked around city blocks once tickets became available for his
lectures. (Until then, the only time I had seen lines that long in
Cambridge was when “Star Wars: The Phantom Menace” came out, the
previous spring.) Between lectures, Hawking and his sizable entourage of
nurses and assistants regrouped in the physics building. I never dared
approach the famous professor myself, but I remember sitting with some
of his assistants late into the night, lost amid the buzz and hum. To be
in the vicinity of Hawking was to be immersed in an extended web of
activity, of people and machines clicking together, a phenomenon
documented in the anthropologist Hélène Mialet’s fascinating study
“Hawking
Incorporated.”

Almost two decades later, I had a different sort of encounter with
Hawking. Last year, several colleagues and I invited him to join a
letter we were
writing,
trying to articulate for a broad audience some of the most significant
insights that cosmologists had developed and tested about the earliest
moments in cosmic history. At first, Hawking objected to the wording of
a particular paragraph. My colleagues, who had known him for decades,
assumed that he would never change his mind; he could be famously
stubborn. Being innocent of that experience, I suggested a modest change
to address his concern. I will never forget the euphoria, the next day,
when I received the e-mail from his assistant saying that Hawking liked
the edit and would co-sign the letter. Hawking might have generated
enduring truths about the cosmos, but at least I could tame a wayward
dependent clause or two.

I imagine that Hawking’s well-known stubbornness helped keep him alive.
He refused to succumb to his disease, outliving his original prognosis
by half a century. But the side of him I think of most is his sense of
humor, and even showmanship. How fitting, I have often thought, that as
he lost control over most of the muscles in his face, his expression
settled into an impish grin. He seemed media-savvy in a way that
Einstein, too, grew to be. As recently as January, 2016, for example,
Hawking held his own—comedically, if not strategically—with the actor
Paul Rudd in a short film about quantum
chess. May his example
continue to inspire young people to beat the odds, and to ask big,
ungainly questions about the universe.

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